1. Field of the Invention
Conical diffusers are routinely used in burner coal nozzles to distribute the coal around the peripheral. Previous experience suggests that if the coal particles can be evenly distributed around the inside surface of the coal pipe, then combustion efficiency will improve. This translates into lower unburned carbon losses and potentially lower nitrous oxide emissions.
2. Description of the Related Art
U.S. Pat. No. 4,380,202 illustrates a mixer for a dual register burner with a diffuser including a reducing area cone, identified as an "oblong-diamond shaped plug", and frusto-conical shroud co-axially surrounding the plug. Plug supports rigidly fix the plug to the inside of the shroud. The plug supports are shaped to minimize the flow resistance to the air entrained pulverized fuel. No further disclosure is provided concerning the number of plug supports and, in the illustration of the reference, only two supports are shown, which are parallel to the axis of the diffuser.
U.S. Pat. No. 4,479,442 is directed to a venturi nozzle for pulverized coal including a divergent flow spreader that is provided with plural swirl vanes.
U.S. Pat. No. 2,912,942 shows a pulverized fuel burner with vanes circumferentially spaced apart. They are triangular-shaped in cross-section and their apexes face the burner axis. The vanes are located on the inner surface of a frusto-conical shroud.